Cartridge magazines which are used for providing a plurality of cartridges to firearms are typically designed to have a predetermined cartridge capacity. After expending the rounds stored in the magazine, the depleted magazine must be replaced with a loaded magazine before continuing to fire the firearm.
By providing a magazine which is able to store a larger number of cartridges as compared to previous magazines, convenience of use of the firearm is increased because less frequent magazine changes will be required. Furthermore, such larger capacity magazines are useful in firearm competition, hunting and other sport uses of firearms to permit the firing of increased number of round before replacement of the magazine becomes necessary. Further, an increased number of cartridges in a magazine is useful in military, police and other law enforcement contexts where the ability to fire even a single additional round without reloading can be of vital importance in many situations.
One method of increasing the cartridge capacity of a magazine would be to simply make the magazine larger, i.e. longer, wider or deeper. However, most such changes require corresponding modifications of the firearm with attendant expense and inconvenience. Thus, it would be preferred to increase the cartridge capacity of the magazine without substantially changing the external configuration of the magazine so that no substantial modification of the firearm is required. In this way, the improved magazine can simply be inserted into the firearm in the same manner as the previous types of magazines were inserted.
An additional reason for preserving the external configuration of the magazine is that certain firearm competitions specify, in their rules, the types of magazines which are permitted. Thus, in many such competitions, magazines with a changed external configuration could not be legally employed. For example, the I.P.S.C. International and U.S. Shooting Rules require that "[t]he magazine used may not extend beyond the butt of the weapon. To qualify this statement, the base plate of the magazine must be within the confines of the butt." Thus, it would be useful to provide a 0.45 magazine which can store more than the eight rounds which are stored by previous 0.45 magazines but which complies with the I.P.S.C. Rules.
Portions of the following describe the present invention as applied to a 0.45 magazine and particularly a 0.45 magazine intended for use in compliance with the I.P.S.C. International and U.S. Shooting Rules. As will be apparent, however, the concepts and principles embodied in the present invention, sometimes with certain modifications, can be used in a wide variety of magazines, including magazines intended for use with bolt action as well as automatic weapons, multiple column as well as single column magazines, and rifles and other firearms as well as hand guns.
In order to provide for a larger number of cartridges, preferably without modifying the exterior configuration of the magazine, it is useful to modify aspects of the interior configuration of the magazine. Some magazines are provided with a follower spring which exclusively resides below the follower. Such a spring is illustrated in U.S. Pat. No. 4,446,645, issued May 8, 1984 to Kelsey, Jr., et al., which discloses making the cartridge follower resilient independently of the follower spring so that this spring action of the follower itself compliments that of the follower spring. Kelsey, Jr. states that the total force exerted by the combined action of the follower and follower spring in unison can greatly enhance the function of the magazine in delivering the cartridges. Kelsey, therefore, was able to provide additional space within the magazine by employing a follower spring having a reduced solid height (and reduced force) and thereby to increase the number of rounds storable in the cartridge from seven to eight. However, the configuration disclosed by Kelsey still requires an irreducible amount of space between the follower and the bottom plate because of the necessity for a storage space for the compressed spring and the necessity for a rear leg or "guide tab" to guide the follower which also occupies space below the follower surface.
Another approach to providing a spring for moving the follower is disclosed in U.S. Pat. No. 2,777,235, issued Jan. 15, 1957 to Hopkins. Hopkins discloses springs constructed to apply a substantially constant force to the cartridges in the removal position. The springs extend in a spiral configuration beneath the follower to be fully coiled when the magazine is empty and to be attenuated to occupy "minimum" space within the magazine when the magazine is full of cartridges. However, Hopkins, similarly to Kelsey, discloses an irreducible amount of space between the follower and the bottom surface of the magazine because Hopkins discloses that even when the magazine is full of cartridges, at least one coil or diameter of the spring extends below the follower. Further, Hopkins discloses a follower having a skirt which occupies space below the follower surface.
Merely, removing the skirt and further attenuating the spring of Hopkins has been found unsatisfactory because removal of the skirt leaves the follower susceptible to rotating or tilting which leads to jamming. Further, merely removing the skirt of Hopkins is unsatisfactory in particular types of magazines because in certain types of magazines, the follower performs a number of functions other than merely moving the cartridges. In a 0.45 magazine, for example, the follower, in addition to having features for preventing rotation of the follower, has features for activating a bolt or slide hold-open mechanism of the firearm at a desired time, has features for assuring that the bolt or slide will not tend to eject the follower from the magazine, and has features to orient and hold the topmost cartridge at a desired angle. Thus, any modification of the 0.45 follower must also provide for performance of the additional functions of the follower.
Complete attenuation of a spring such as that in Hopkins, without further changes, has been found unsatisfactory in many cases because the fully stretched spring may not always move into the desired spiral configuration underneath the follower as the follower moves upward. Further, the attenuated spring creates a force on the follower which acts in a direction substantially different from the upward direction, and usually acts to move the follower towards one of the end or side walls. Both the tendency to not assume the desired coil configuration and the tendency to apply force towards a side or end wall leads to loss of spring lifting power. Loss of spring lifting power is made even more serious by providing an additional cartridge and thus additional weight which must be lifted, e.g., as in increasing the number of 0.45 cartridges from eight to nine.